Learning to play tennis or the piano, to juggle or to play the Rumikub with one single hand elicits changes in the brain at many different levels, over different timescales and in different areas. The primary motor cortex, an area highly involved in the control of our movements, is especially important for skill learning. Therefore, scientists have focused on this brain area in order to understand the changes taking place in the brain during learning.

Until recently, the following cascade of events was thought to underlie skill learning (Monfils et al. 2005). Motor training induces synaptic plasticity through neural signaling, gene transcription and protein synthesis. Synaptic plasticity consists in change of excitability of some neurons in order to make them either more likely (long-term potentiation) or more unlikely (long-term depression) to fire. These changes in synaptic plasticity make some specific networks stronger and lead to some reorganization of the local circuitry (motor map reorganization). As a result of this reorganization, microstimulation of the motor cortex results in different movement patterns than before the learning of a skill. This change in local circuitry also involves an increase in the number of synapses (and spines) per neurons, a phenomenon called synaptogenesis. Synaptogenesis corresponds to the formation of new connections between some pairs of neurons and was thought to occur late during the training, i.e. when the performance is already high and the number of errors low.